1. Field of the Invention
The present invention relates to a method for regenerating supported iridium-containing hydrocarbon conversion catalysts. In particular, the present invention relates to a process for the controlled regeneration of a supported iridium-containing hydrocarbon conversion catalyst that has been deactivated by the deposition of carbonaceous residues thereon during contact with a hydrocarbon feed stock at elevated temperatures.
2. Description of the Prior Art
The deactivation of noble metal-containing hydrocarbon conversion catalysts, due to the deposition of carbonaceous residues thereon during use, is a well known phenomenon. Catalyst deactivation is particularly acute with respect to supported noble metal containing catalysts used in the hydroforming of naphtha feed stocks.
Noble metal containing reforming catalysts, in particular platinum-containing catalysts, have traditionally been arranged by burning the coke or carbonaceous residues from the catalyst followed by a redispersion operation whereby the platinum contained on the catalyst, which is agglomerated with loss of surface area during the burning operation, is redispersed by treatment with chlorine or other halogen providing reagents, alone or in combination with oxygen, at elevated temperatures. The relatively simple techniques employed for the redispersion of platinum are not directly applicable for the residpersion of iridium. One of the reasons for this fact is that unprotected iridium tends to agglomerate to low surface area iridium metal and/or iridium oxide crystallites when exposed to halogen-free, oxygen at elevated temperatures. Procedures have been developed for the facile redispersion of iridium following a carbonaceous residue burning operation. However, conducting the redispersion operation is relatively time consuming and increases the amount of time that a commercial unit is not in use.